The requirement arises frequently in traffic engineering to transport persons over very long distances, which requires a time in the order of magnitude of ten hours or more. In railroad engineering, sleeping compartments have been provided for this purpose, which contain one or more beds over each other and in which eventually several groups of lying support surfaces are provided on walls situated opposed to each other.
In this known principle of transportation of persons in a recumbent position, one starts out from a relatively large available space. In recent times however, air transportation too has developed to such an extent, that many passengers can be transported with large capacity aircraft over very long distances and thus the problem arises here too to create greater comfort and healthier conditions of transportation. Actually it is customary to provide adjustable passenger seats in aircraft which make it possible for the passenger to assume a semirecumbent position. On long distance flights with a flying time in the order of magnitude of ten hours, however, such passenger seats are totally inadequate, and the unnatural body position in itself, leads to extreme exhaustion, if not to health damage of the passengers.
It is true that sleeping bunks have been built into aircraft, similarly as in ship building to make a rest for the crew possible on long duration flights. However, the application of this principle is out of question for the passengers to be carried, as fixed, built-in sleeping bunks would on the one hand increase the flying weight considerably, and on the other hand would essentially limit the possible number of passengers to be transported.